Light weight panels commonly formed of a sandwich of two flat facings and an intermediate "core" structure bonded together are often used as flooring, bulkheads and the like in commercial aircraft. Such sandwich panels possess the high strength and stiffness and low weight characteristics desired in aircraft. Panels as indicated are used with known fasteners; these are affixed to these panels in a variety of ways. The fasteners permit bolts, spacers, threaded inserts and other attaching devices to be used to fasten these panels to support structures in an aircraft as well as to permit other structures and accessory equipment to be supported on and maintained in a fixed location on the aircraft floor. A large variety of fasteners for such applications have been marketed and sold by the ShurLok Company, Irvine, Calif., U.S.A., the assignee of the present invention.